A collision alarm system disclosed in a patent document 1 (JP2004-231017 A) estimates the degree of concentration of the driver, and suppresses a collision alarm when the degree of concentration is high. A driving support system disclosed in a patent document 2 (JP2005-209073 A) adjusts the timing of presentation of information about the position of a stop sign and a forward obstacle, in accordance with various factors of the driver (such as age, sight and driving experience) capable of affecting the alertness, and response speed of the driver.